1. Field of the Invention
The invention relates to a manufacturing method of a thin film transistor and to a thin film transistor and also to a display. In more detail, the invention relates to a manufacturing method of a thin film transistor of a top gate type using an organic semiconductor layer as a channel layer and to a thin film transistor and also to a display using the same.
2. Description of the Related Art
A thin film transistor (TFT) is widely used as a pixel transistor in electronic circuits, in particular flat panel displays of an active matrix type.
At present, the majority of thin film transistors is an Si based inorganic semiconductor transistor using amorphous silicon or polycrystalline silicon as a semiconductor layer. Since the manufacture of the same employs fabrication requiring a vacuum treatment chamber such as chemical vapor deposition (CVD) for the formation of a semiconductor layer, the process costs are high. Also, since a heat treatment at high temperatures is necessary, a substrate is required to have heat resistance.
On the other hand, in a thin film transistor utilizing an organic semiconductor, it is possible to coat and fabricate an organic semiconductor layer which becomes a channel layer at low temperatures. For that reason, not only such is advantageous for realizing low costs, but also it is possible to achieve the formation on a flexibly substrate with low heat resistance such as plastics.
Of the foregoing thin film transistors, in particular, a thin film transistor of a top gate type is studied as a drive device of an active matrix type in display devices such as electronic paper. In the case of the top gate structure, a channel layer is disposed in a side of a back side substrate with respect to a gate electrode as compared with the case of a bottom gate structure, and therefore, there is brought an advantage that influences of a potential of a pixel electrode against the channel layer can be made small. In the former case, as a forming method of the gate electrode, there is often employed an example in which a metal such as gold is subjected to pattern formation via a shadow mask by, for example, vapor deposition (see, for example, Advanced Function Materials, (United States) 2003, Vol. 13, p. 199; and Applied Physics Letters, (United States) 2002, Vol. 81, p. 1735 (Non-Patent Documents 1 and 2)).